ExhaustGasTemperatureMonitorForAnInternalCombustionEngine

ELEC399

FINALREPORT

GroupID:17

Supervisor:TomTiedje

SubmittedonDecember3rd,2012

Dept. Electrical and Computer Engineering

University of Victoria

All rights reserved. This report may not be reproduced in whole or in part, by photocopy or other means, without the permission of the author.

JamesBoileau V00738149Boileauj@Uvic.ca

SawyerPahl V00731863SawyerPahl@gmail.com

LudiLing V00737324LingL@Uvic.ca

GarvinRuus V00688254Gdruus@gmail.com

KurtisNewman V00241647Kuritsn7@gmail.com

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TableofContents1 Introduction.............................................................................................................................1

1.1 Objective............................................................................................................................1

1.2 ExhaustGasTemperature..................................................................................................1

1.3 EngineTuning....................................................................................................................1

1.4 EGTMonitoringSystem.....................................................................................................2

2 Design.......................................................................................................................................3

2.1 TemperatureSensor..........................................................................................................3

2.1.1 Mounting.....................................................................................................................72.2 Amplifier............................................................................................................................8

2.2.1 EGTQuadChannelAmplifier.......................................................................................92.2.2 AD595AmplifyingChip..............................................................................................102.2.3 DesigningOurOwnAmplifier....................................................................................11

2.3 DataRecording................................................................................................................11

2.3.1 DesignJustification....................................................................................................112.3.2 FutureConsiderationsforanExternalDataLogger..................................................132.3.3 ArduinoUnoR3:........................................................................................................13

3 Conclusions............................................................................................................................15

3.1 ConcludingRemarksandFutureWork............................................................................15

3.2 ProjectMilestones...........................................................................................................15

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1 Introduction

1.1 ObjectiveThe objective of this project is to design a system to monitor and display the exhaust

gas temperature (EGT) of an internal combustion engine. The system will be used by

the UVic Formula SAE team to monitor the temperature of the exhaust gas in their car’s

engine with hopes that the data can give insight to the performance of the engine. It is

possible that this data can result in better engine tuning and better overall performance

of the engine.

1.2 ExhaustGasTemperatureThe ability to measure the EGT’s of each cylinder in an internal combustion engine can

provide useful data when it comes to engine tuning. The EGT can provide insight on the

cylinder’s air-fuel ratio (AFR), which is an important characteristic when it comes to

performance. If not enough fuel is injected into the cylinders during the combustion

process, the exhaust gas will be much hotter. This is known as a “lean” air-fuel ratio.

Conversely, if there is too much fuel in the combustion process, the exhaust gas will be

cooler. This is known as a “rich” air fuel ratio. An air-fuel ratio that is too lean or too rich

can result in loss of performance in the cylinder. Additionally, if the air-fuel ratio varies

significantly between each cylinder, then the fuel injection process is not distributing fuel

evenly, resulting lower performance of the engine.

By monitoring EGT, the engine can be tuned in such a way to optimize engine

performance.

1.3 EngineTuningWhen tuning the engine we monitor the engine using a Dynamometer (dyno). The

combination of the dyno and the car’s Engine Control Unit (ECU) allows us to monitor

several engine characteristics simultaneously. The ECU used is called Megasquirt3

(MS3) and will be briefly described later in this report. The characteristics observed are

gathered from various sensors throughout the vehicle and output to a Software platform

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offered by Megasquirt3 (MS3). During one engine test, it is possible to simultaneously

observe the following vs time:

- Manifold Air Temperature (MAT)

- Manifold Air Pressure (MAP)

- Coolant Temperature (CLT)

- Throttle Position (TPS)

- Air to Fuel Ratio (AFR)

- Revolutions Per Minute (RPM)

- Horsepower (HP)

- Torque (TRQ)

Each of these characteristics provides insight into how the engine is performing. With this data we can tune the engine with the MS3. There are 3 things we can adjust:

- Spark Timing,

- Injector Timing

- Volumetric Efficiency (Volumetric efficiency is a ratio of the quantity of fuel and air

mixture that enters a cylinder during the intake stroke to the actual capacity of the

cylinder in static conditions.)

It is our hope that by adding EGT to the list of measurable characteristics, the engine

can be tuned even more effectively then it already is.

1.4 EGTMonitoringSystemIn order to achieve effective EGT monitoring, our system will need to consist of:

1. Temperature sensors to be placed in the exhaust manifold.

2. Signal amplifier used to amplify the analog temperature signal

3. Data logging/displaying system to display the data.

There are several factors to consider with each of these components. This report will

discuss our design in detail and provide information on future plans for this project.

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2 Design

2.1 TemperatureSensorWhen selecting a sensing method for the EGT, a number of factors needed to be taken

into consideration. The temperature inside the exhaust manifold can range from 600-

1200 degrees Celsius. The sensor would need to be accurate within this range, and

also be able to withstand these high temperatures for an extended period of time

without deteriorating. The formula SAE racecar is also prone to experience high g

forces during it’s operation, whether from normal track usage or potential crashes,

vibrations, etc. The ideal sensor would need to be durable enough so that the

probability of failure under these circumstances is very low. Also, the sensor would need

to be small enough so that it does not significantly disrupt air flow through the exhaust

manifold, which could hinder performance. Other factors to consider include price, ease

of mounting, margins of error in measurements, and voltage difference per degree.

With these considerations in mind, we came to the conclusion that a K-type

thermocouple would be the ideal sensor to use for this project. A thermocouple is made

from two different conductors that are joined together and produces a voltage near the

point of contact. This voltage is dependent on the difference of temperature of the

junction in comparison to other areas of the conductors, and can be used to measure

temperature. Since thermocouples are simply made of two different conducting wires,

they are extremely durable and small enough so that the exhaust flow will not be

disrupted. They also allow for a wide temperature sensing range, from -200 to 1260

degrees Celsius, a fast response time, and relatively low initial cost. The main downfall

of a thermocouple is that the error can be relatively high, generally around 0.75%. The

alternatives, however, also have limitations. Thermistors do not generally allow for a

high enough temperature range, and although RTD’s will work, and are more accurate,

they are costly, less durable, and have a narrower temperature range. Since typical

variations of temperature between cylinders are around 38 degrees Celsius, an error of

0.75% would still give meaningful results, and by taking the average of multiple

measurements, the error can be significantly reduced.

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A type K thermocouple uses the nickel-based alloys Chromel and Constantan for the

conductors. It is durable and has good corrosion resistance due to being nickel based,

making it ideal for use in an engine. It is also cost effective, and is the most common

thermocouple available. Type K thermocouples typically have a temperature range from

-200 to 1260 degrees Celsius, well within our required range, are cheaper than some of

the alternatives, and have a reasonable tolerance within our intended range. It has an

exponentially increasing thermoelectric voltage, making the difference in voltages easier

to measure and more accurate at higher temperatures. This is ideal since it will normally

be operating at higher temperatures. In the range from 293 degrees to 1250 degrees

Celsius, the tolerance is +/- 0.75%. The graph below shows the voltage output as a

function of temperature for a variety of thermocouples.

Figure 1 - Voltage vs temperature dependence for a range of different thermocouples.

Our choice to use a type-K thermocouple was solidified by the fact that, for measuring

automotive EGT, type K thermocouples are generally the industry standard sensing

mechanism. Because of this we know it is proven to be effective, and there is more

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information available on measuring EGT with these sensors than any other type. When

browsing for a specific product to use we found a cost effective kit that includes four

Stinger Hyper Response EGT probes, an amplifier, and mounting hardware. The price

of the kit is $399.95, and is not much more expensive than purchasing the sensors

separately. One advantage of using a kit is that the components are preselected to work

properly together. For example, when connecting a thermocouple to any type of

instrument, the connector has to be made of the same alloy as the thermocouple

otherwise there will be an error in the measurement. This kit takes this into

consideration and comes with compensated connectors to match the alloy used in the

sensors. The sensors are high quality with all the required specifications, and since

mounting hardware is included, installing the sensors and amplifier will be easier. We

believe the finished product will be less prone to errors if we use a kit as opposed to

mismatched products, or designing our own amplifier and mounting hardware.

Specifications of sensing capabilities:

• Exposed tip design allows for very fast response time of 0.6 seconds.

• Temperature measurement range is between 0 – 1250 degrees Celsius.

• Sensitivity of 41 microvolts per degree C. This becomes 4 mV per degree C

with amplification.

• 72” wire length.

• Positive leg is non-magnetic (Yellow), negative leg is magnetic (Red).

• Appropriate for use in oxidizing or inert atmospheres at temperatures up to

1260°C.

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Below is a graph of the output voltage of a similar type K thermocouple vs temperature,

as well as a graph depicting the deviation from the straight line approximation at any

given temperature. From these graphs we see that in our intended range, from 600 to

12000 degrees C, the output voltage vs temperature is approximately linear, with a

maximum deviation of about +/- 10 degrees C. Using information from these graphs we

may be able to better calibrate the sensors.

Figure 2 - K type thermocouple output voltage as a function of temperature

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Figure 3 - K type thermocouple deviation from straight line approximation vs temperature

2.1.1 MountingThe sensors will be mounted 1.5 inches below the cylinder port. Installation consists of

first drilling and tapping a 1/8 inch hole in the exhaust manifold. A 1/8 inch NPT steel

bung is centered on the tapped hole and welded to the exhaust manifold. This bung is

threaded on the inside and once welded to the manifold, the EGT sensor can be

screwed into the bung. The tip of the sensor fits through the 1/8 inch hole and into the

exhaust manifold. The sensors should be placed as far away from any sources of

electromagnetic interference (EMI) such as spark plugs, wires, and coils as possible.

EMI noise may be induced into the probe wires. The figure below shows the tip of a

thermocouple, and the threading that would be screwed into the bung.

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Figure 4 - Thermocouple sensor tip

2.2 AmplifierDue to the thermocouples outputting their own voltage signal in the order of microvolts,

we need to either use an extremely sensitive voltmeter or amplify the signal. In order to

get a useful voltage reading from the thermocouples that are accurate for a 0-5V input,

which is the voltage reading we need for the onboard Mega Squirt 3 computer, we need

to amplify the signal. There were a few different options we explored en route to finding

the optimal amplifier. These options consisted of designing our own amplifier, or using

one of two prefabricated amplifiers; the EGT Quad Channel Amplifier (specially

designed for this application) or the AD595 Amplifier. We had to carefully analyze which

would be the most suitable option taking into consideration the following characteristics:

• Amplifying to the 0-5V voltage we need and the errors associated with each one

• Temperatures that the amplifiers can withstand if mounted on the FSAE car

• Cost

• Time constraints

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2.2.1 EGTQuadChannelAmplifierThe EGT Quad Channel Amplifier amplifies the signal from an ungrounded Type K

thermocouple up to a 0-5V signal. The onboard MS3 computer can read this voltage

signal. Each thermocouple after amplification outputs a 4mV signal for every degree

Celsius of change. If powered by 14.5-32V the Quad Amplifier can achieve the full

temperature reading range of the Type K thermocouples (0°C to 1250°C). A graph of

maximum temperature range versus power voltage is seen in figure 2.2.1.

Figure 5: Max Measurable Temperature vs. Power voltage

The EGT Quad Channel Amplifier is restricted to an external ambient exposure

temperature of 80°C. If the chip is exposed to higher than 80°C, the plastic enclosure

may suffer serious damages. Due to the enclosure needing to be mounted on the FSAE

car, it will most likely incur temperatures upwards of 50°C but we feel that we will be

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able to find a mounting placement where it will not be exposed to greater than 80°C. If

that is not the case, providing heat shielding might be necessary. A perk of using the

EGT Quad Channel Amplifier is that due to it being an analog signal it samples at an

infinite frequency. Thus, the amplifier has a higher slew rate than the Type K

thermocouple so the thermocouple sensor and not the amplifier limit response time.

If the amplifier gain error and offset error are calculated beforehand by zeroing the

reading (putting the thermocouples in ice water at 0°C – voltage should read 0V). Any

offsets and errors can be recorded and used in the temperature calculation in order to

get precise readings.

When calibrating the temperature for this amplifier, we use the following equation:

Temperature °C = (Voltage / (0.004 * (1 + amplifier gain error))) - offset error

(Where the 0.004 in the function is the nominal 4mV / °C)

Lastly, the EGT Quad Thermocouple Amplifier requires no designing time with it being

prefabricated, and costs $399.99. This package includes 4 Type K thermocouples.

2.2.2 AD595AmplifyingChipThe AD595 Amplifying Chip was another possible candidate we explored for amplifying

the 4 voltages being outputting from the thermocouples. When reading into this type of

chip and comparing it to the EGT Quad Channel Amplifier, there were a few

discrepancies that put us in favour of using the EGT Quad Channel Amplifier.

Firstly, the cold junction errors of the AD595 are relatively high. Voltage outputs coming

from the amplifier were very dependent on the chip being in thermal equilibrium. If the

chip was exposed to greater than 50°C there was a high possibility of damages and

cold junction error. This compared to the EGT Quad Channel Amplifier was 30°C lower.

This along with the fact that the AD595 does not come in a Quad Channel package with

4 Type K thermocouples included is enough reason to choose the EGT Quad Channel

Amplifier.

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The cost of purchasing this chip is around $40. However on top of buying the chip the K

Type thermocouple wire has to be ordered. This costs $120 per 30 m.

2.2.3 DesigningOurOwnAmplifier In order to design our own amplifier we would have to meet with specialty IC chip

manufacturers and spend time coming up with a prototype and then optimizing it until

we had a final product made. This could take months or even years. Unfortunately due

to time constraints, this is not the best option for this project.

After exploring three possible solutions for amplifying our voltage signal from the

thermocouples, we came to the conclusion that the most feasible solution is the EGT

Quad Channel Amplifier.

2.3 DataRecordingIn order to interpret the EGT data incoming from each temperature sensor, a

microcontroller will need to be incorporated into the system. The microcontroller needs

to be able to take in at least 4 analog inputs, one for each sensor, as well as be able to

output the data to a display to give the user visibility to the sensor readings. Currently

there are two options available for consideration:

1. Using the car’s existing ECU, Mega-Squirt 3 Engine Management System.

2. Using an external Arduino microcontroller.

2.3.1 DesignJustificationWe decided to use the car’s existing ECU, Mega-Squirt 3 in order to collect the data for

the EGTs. The MS3 has a total of 5 available analog inputs. The FSAE team currently

uses the MS3 interface to data log Coolant Temperature, Manifold Air Temperature, Air

to Fuel Ratio, and Throttle Position. This leaves only one remaining input. We could

data log one cylinder at a time; however, we want all the cylinders to be operating within

similar temperatures. The best way to ensure each cylinder is undergoing similar

combustion is to test them at the same time. This means that we will unplug 3 of the

other data logging sensors on the vehicle when testing for the 4 cylinders EGTs.

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The MS3 has onboard data logging capabilities and saves the data to an SD card,

which can then be read on a laptop using MS3 software. The MS3 is also able to

communicate live data through a serial connection to a laptop. The main reason to use

our current ECU to record EGTs is that the MS3 software that we use has an interface

built in for EGTs. A sample result from an 8-cylinder engine is shown below in Fig 1.

This figure demonstrates how the EGTs can be displayed simultaneously with Throttle

Position and Revolutions per Minute using the MS3 interface.

Fig 6 - Example of EGT reading using MS3 for 8-cylinder engine

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2.3.2 FutureConsiderationsforanExternalDataLoggerIdeally we would want to log the data for the EGTs as well as the other four inputs

mentioned above. This is the main motivation for using an external Data Logger.

However, our external Data Logger is a work in progress for the FSAE Electrical team.

The FSAE Electrical Team is currently developing a Data Logger using an Arduino Uno

R3. This external Data Logger will be valuable to the team for more than just EGTs.

The FSAE team is aiming to test both the EGTs and the Arduino Data-Logger

simultaneously next semester. Currently the Arduino creates a mls The two projects

are an adequate fit because our current MS3 ECU contains the ability to interpret

Thermocouple Analog signals and display the results. In the future we will be able to

import the data from the ECU into excel and compare it to the excel file supplied by the

Arduino. We can use this comparison to see whether or not our Arduino Data-Logger is

working or accurate.

2.3.3 ArduinoUnoR3:

The Arduino Uno is a microcontroller board. It has 14 digital input/output pins and 6

analog inputs. It can be connected to a computer using a USB cable or can be powered

by DC.

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Microcontroller ATmega328

Operating Voltage 5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

Digital I/O Pins 14 (of which 6 provide PWM output)

Analog Input Pins 6

DC Current per I/O Pin 40 mA

DC Current for 3.3V Pin 50 mA

Flash Memory 32 KB (ATmega328) of which 0.5 KB used by bootloader

SRAM 2 KB (ATmega328)

EEPROM 1 KB (ATmega328)

Clock Speed 16 MHz

Table 1 – Arduino Uno Microcontroller Specifications

Cost: $29.95

The FSAE team already has an Arduino Uno R3. However, should we wish to

simultaneously data log more than 6 analog signals at once the FSAE team could run

two separate data loggers.

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3 Conclusions

3.1 ConcludingRemarksandFutureWorkThe design discussed in this report will provide a solution to the EGT monitoring

system. It is anticipated that this design be implemented in the future to provide the

UVic Formula SAE team with better insight to their engines performance resulting in

improved engine tuning. During the design process, factors like cost, equipment

availability, existing data logging systems, and performance were all taken into

consideration. Due to the limited budget of the Formula SAE team, cost of equipment

affected our decisions drastically. It is recommended that the EGT Quad Channel

package be purchased for the price of $399.99. It may not be the most inexpensive

solution but the convenience of having a package kit justifies this purchase. It is our

hope that the Formula SAE team will approve this design and the system will be built,

tested and operational by February 2013. It is anticipated that the EGT monitoring

system will ultimately result in improved engine performance and better results for the

FSAE team at competition, however it is not yet known whether or not the EGT system

will provide any useful data, or if the engine performance can be improved with this

data.

3.2 ProjectMilestonesTable 1: Summary of accomplishments and dates

Accomplishments Completion Date

First Group Meeting 2012-11-28

Dr. Tiedje agrees to be supervisor 12-10-10

Second group meeting 12-10-12

Interim report submitted 12-10-16

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Meeting with Dr. Tiedje 12-11-16

Third group meeting 12-11-26

Website design 12-12-03

Final report submitted 12-12-03